When an antenna of a wireless communication device such as a cellular telephone is retracted, it is sometimes desirable to alter the power of a radio frequency signal that is coupled to the antenna, so as to increase or decrease the amount of radio frequency energy that is applied to the antenna. When a whip antenna is used, there is also a need to add passive electrical loading at the end of the antenna when the antenna is retracted. There are known techniques of accomplishing these objectives, but they require several mechanical and electrical parts. In one prior art technique used for an antenna having a helical portion, a matching circuit is connected to the feed point of the antenna and the opposite end of the antenna is grounded when the antenna is retracted. This technique which is described in U.S. Pat. No. 5,739,792, entitled "Wireless Communication Device with Electrical Contacts", that issued to Hassemer et al. on Apr. 14, 1998 (hereinafter, "Hassemer"), and that is incorporated herein by reference, uses two independent switch mechanisms (reference numbers 32, 38) formed of conductive spring metal that are spring loaded and that each make contact to the antenna in the retracted position, plus a conductive spring element (36) that is in contact with the antenna in both the retracted and extended positions. This arrangement works well enough but is more complicated than is necessary for a whip antenna that benefits from a load circuit that is connected only in the retracted position.
Thus, what is needed is a simpler and less costly technique of adding an electrical load to a retracted antenna and changing the power of a transmit signal coupled thereto when it is retracted.